Melt processible fluoropolymers such as tetrafluoroethylene/perfluoro(alkyl vinyl ether) copolymers (PFA) and tetrafluoroethylene/hexafluoropropylene copolymer (FEP) have excellent heat and chemical resistance. However, these fluoropolymers also have very high electrical resistance at their surfaces, and as a result they easily accumulate static charge, and are slow to dissipate the charge.
In electrostatic copy machines, rotating parts such as, belts, tubes, and rolls, made of melt processible fluoropolymers are used. Because of static charge accumulation on the parts, image quality can be affected adversely. Therefore it is desirable that these articles have antistatic character, by which is meant that they have sufficient surface conductivity to prevent accumulation of static charge to the point that the static charge affects the good operation of the apparatus, such as a copy machine.
Melt processible fluoropolymer-based wafer carriers used in the semiconductor production process, chemical solution pipelines, and parts such as joints, are generally used in service that requires a high degree of cleanliness. If such articles accumulate static charge, they can attract microparticles from the atmosphere to the detriment of the quality of parts or materials with which they come in contact. Furthermore, in pipelines transporting combustible liquids, the passage of the liquids through the pipe generates static electricity, which can lead to sparking, a fire hazard
Conventionally, antistatic fluoropolymer compositions are made by blending with an electrically conductive powder, and molding articles therefrom. For example, in U.S. Pat. No. 4,664,846 and Japanese Kokai Patent Nos. SHO 62[1987]-223255 and HEI 2[1990]-255751, polymer compositions made from fluoropolymer mixed with electrically conductive materials such as carbon black and carbon fiber, fibrous conductive titanium oxide, and zinc oxide are disclosed.
However, imparting antistatic properties to fluoropolymers by mixing with electrically conductive materials can give rise to contamination if the added material is released, such as by abrasion or wear.
There is a need for melt processible fluoropolymers able to dissipate static electrical charge without the need for blending with conductive powders.